Steam-explosion-modified optimization of soluble dietary fiber extraction from apple pomace using response surface methodology

To make full use of apple pomace, pretreatment with steam explosion (SE) was investigated to determine its effects on the yield and functionality of soluble dietary fiber (SDF). Response surface methodology (RSM) was used to optimize the effects of SE parameters. According to the quadratic polynomial model, the optimum SE parameters were as follows: steam pressure, 0.51 MPa; residence time, 168 s; and sieving mesh size, 60. Under the optimized conditions, the SDF yield from apple pomace after SE was 29.85%, which is 4.76 times the yield of SDF (6.27%) in untreated apple pomace. The SDF prepared with SE also exhibited higher functionality values. Scanning electron micrographs (SEM) indicated that the SDF surface from apple pomace was poriferous, rough and lax after SE treatment; therefore, it can be concluded that the SDF morphology was altered by the steam explosion.